Percussion to direct keying switching circuit for an electrical musical instrument

ABSTRACT

In an electrical musical instrument having a plurality of selectively played keys each for connecting a tone generator keyer to a source of keying voltage through a related percussion keyer circuit, a percussion to direct keying switching circuit for selectively providing percussion and direct keying operation of all of the tone generator keyers by operation of a single control switch.

United States Patent [191 S chrecongost PERCUSSION TO DIRECT KEYING SWITCHING CIRCUIT FOR AN ELECTRICAL MUSICAL INSTRUMENT [75] Inventor: Ray B. Schrecongost, Park Ridge,

[73] Assignee: Hammond Corporatiom Deerfield,

Ill.

[22] Filed: June 111, 11973 [21] Appl. No.2 368,879

[ 1 June 28, I974 3,493,668 2/1970 Bunger 84/1.13 3,544,699 12/1970 Harris 84/1.26 3,549,779 12/1970 Bunger 84/l.26 3,580,980 5/1971 Uetrecht 84/1.26 X 3,617,601 11/1971 Krueger 84/1.01 3,626,074 12/1971 Hiyama 84/1.01 3,626,075 12/1971 Hiyama 84/l.13 3,634,594 l/l972 Hiyama 84/1.26 X 3,651,730 3/1972 Adachi 84/1.26 X 3,657,463 4/1972 Hiyama 84/126 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Stanley J. Witkowski Attorney, Agent, or FirmLowe1l C. Bergstedt [52] US. Cl 84/1.13, 84/1.26, 84/D1G. 12 [51] Int. Cl. Gl0h 1/02 [58] Field of Search 84/l.13, 1.26, DIG. 12, [57] A S In an electrical muslcal instrument having a plurality 84/DIG. 23, 1.01

of selectively played keys each for connecting a tone [56] References Cited generator keyer to a source of keying voltage through a related percussion keyer circuit, a percussion to di- UNITED STATES PATENTS rect keying switching circuit for selectively providing 2,483,823 10/1949 (ICOl'gC 84/1.26 percussion and direct peration of a" of the tone generator keyers by operation of a single control ra m 3,435,123 3/1969 Schrecongost 84/1.26 Swltch' 3 3,446,904 5/1969 Brand et a1. 84/ 1.13 5 Claims, 1 Drawing Figure -25vorrs' VOLTHGE 15 sol/RC5 TONE s/a/vm.

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{YI? i 10 7 7 7 7 /1 29 PERCUSSION TO DIRECT KEYING SWITCHING CIRCUIT FOR AN ELECTRICAL MUSICAL INSTRNT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electric circuits operable to control percussion keying of musical tone signals in electrical musical instruments.

2. Description of the Prior Art In an electrical musical instrumentsuch as an electronic organ having a plurality of selectively played keys each for switching or connecting a known tone generator keyer to a source of DC. keying voltage, it is frequently desirable to provide percussion keying of musical tone signals in order to produce musical tones which simulate the sounds produced by certain percussion musical instruments. Known percussion keyer circuits typically comprise a capacitor in series with a key and a corresponding tone generator keyer, the capacitor being charged upon key closing through a resistance connected in parallel with the tone generator keyer. In operation, when the key is closed, the voltage at the tone'generator keyer abruptly rises to the maximum keying voltage value and then decreases at a predetermined rate as the series capacitor is charged through the resistor, thereby percussively keying the musical tone signal. Such a circuit typically also includes a resistance of relatively low value connected between the key end of the capacitor and ground, and a gating means or diode connected between the keyer end of the capacitor and ground, these elements to-' gether being operable to provide a path for rapidly discharging the capacitor upon opening their corresponding key to insure that adequate keying voltage will be provided upon a subsequent actuation of that key.

In such electrical musical instruments, it is, however, essential to provide means for directly keying the tone generator leyer without percussive modification of the keying voltage waveform envelope. Prior systems known to applicant for selectively providing percussion and direct keying operation of all of the tone generator keyers generally require an additional contact for each key for selectively applying the unmodified keying voltage directly to the tone generator keyer. For use with an electrical musical instrument such as a typical electronic organ having 61 keys, such systems require considerable duplication of manufacture and assembly effort.

SUMMARY OF THE INVENTION The present invention overcomes the shortcomins of prior systems known to applicant by providing a percussion to direct keying switching circuit wherein percussion and direct keying operation of all of the tone generator keyers are selectively determined by the operation of one single control switch.

The percussion to direct keying switching circuit of the present invention is adapted for use with an electrical musical instrument having a plurality of selectively played keys each for connecting a tone generator keyer to a source of keying voltage through a related percussion keyer circuit comprising a capacitor in series with the key and gradually charged upon key closing through a first resistance connected in parallel with the keyer and wherein the capacitor is in circuit with a sec- 0nd resistance having a relatively low value connected to the key end thereof and a first gating means or diode connected to the keyer end thereof, the second resistance and the first gating means or diode being interconnected at a junction and being operable, when the junction is grounded, to rapidly discharge the capacitor upon opening the key and further operable, when the junction is isolated from ground, to provide a path shunting the capacitor for direct keying. The percussion to direct keying switching circuit comprises a plurality of second gating means or diodes and a single control switch, each of the second diodes being in circuit with one of the junctions and the control switch, the control switch being in circuit with ground and a source of second voltage of value at least equal to the keying voltage and being selectively operable to ground each junction in circuit therewith and, in the alternative, to isolate the same from ground potential by reversely biasing the second diode with the second voltage. Percussion and direct keying operation of all of the tone generator keyers are selectively determined by operation of the single control switch.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a schematic diagram illustrating the basic features of the preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the preferred embodiment of the present invention, which is schematically illustrated in the FIGURE, a plurality of keys 10 (only a few of which are illustrated for simplification) are shown, each for connecting a corresponding tone generator keyer 11 to a source of keying voltage provided at a keying bus 12 which is connected to a voltage source at terminal 13 through leads 14 and 16. Terminal 13 is in turn connected to a supply having a voltage of -28 volts, which is an example of a suitable source of keying voltage in an electrical musical instrument such as an electronic organ. Each keyer 11 may typically comprise means for gating a musical tone signal from a musical tone signal source (not shown) to a keyer output in response to the application of a DC. keying voltage, such as the device disclosed in US. Pat. No. 3,636,231 to Schrecongost et a1 entitled D.C. KEYED SYNTHESIS ORGAN EM- PLOYING AN INTEGRATED CIRCUIT.

Each key 111 is operable to provide a DC. keying voltage. to its corresponding tone generator keyer 11 through a well-known percussion keyer circuit 17 and leads 18 and 19. Each percussion circuit 17 comprises a capacitor 21 in series with the key 10 and gradually charged upon key closing through a first resistance 22 connected in parallel with the keyer 11. The capacitor 21 is in circuit with a second resistance 23 having a relatively low value connected to the key end of the capacitor 21 and a first gating means or diode 24 connected to the keyer end of the capacitor, the second resistance 23 and the first diode 24 being interconnected at a junction 25. When this junction 25 is grounded, resistor 23 and diode 24 provide a path for rapidly discharging capacitor 21 upon opening the key 111 to insure that adequate keying voltage will be provided upon a subsequent actuation of the key. When junction 25 is isolated from ground, a path shunting the capacitor is provided through lead 18, resistor 23, junction 25, diode 24, and lead 19 for direct keying without percussive modification of the keying voltage waveform envelope. An additional capacitor 26 is usually included to eliminate the undesirable effects of transients or to provide sustain as desired.

The component values indicated in the FIGURE are representative of typical values found in a preferred working embodiment of the present invention, but it will be recognized, of course, that the operation of the percussion to direct keying switching circuit is not restricted to the component and voltage values shown.

The percussion to direct keying switching circuit according to the present invention comprises a plurality of second gating means or diodes 27 and a single control switch 28, each of the second gating means or diodes 27 being in circuit with a corresponding junction 25 by means of a lead 29 and in circuit with the control switch 28 by means of leads 31, 32 and 33. The control switch 28 is in circuit with a ground lead '34 and a source of second voltage on lead 36 of value at least equal to the keying voltage at terminal 13; in the preferred embodiment, lead 36 is conveniently connected to lead 14 in circuit with the source of keying voltage at terminal 13.

When the single control switch 28 is in the percussion mode, lead 33 is connected to ground lead 34 with the result that all of the junctions 25 are grounded because all of the second diodes 27 are forward biased. In this mode of operation, each resistor 23 and diode 24 are together operable to provide a path for rapidly discharging their corresponding capacitor 21 upon key opening.

Alternatively, when the single control switch 28 is in the direct keying mode, lead 33 is connected to lead 36 with the result that all of the junctions 25 are isolated from ground because all of the second diodes 27 are reversely biased by the second voltage on lead 36. In this mode of operation, each resistor 23 and diode 24 are together operable to provide a path shunting the capacitor 21 for direct keying without percussive modification ofthe keying voltage waveform envelope.

.It is apparent that percussion and direct keying operation of all of the tone generator keyers 11 are selectively determined by operation of the single control switch 28.

I claim:

1. In an electrical musical instrument:

a source of keying potential;

a tone generator keyer having a keying input lead;

a keying circuit coupled to said keying input lead;

and

a keyswitch coupled between said source and said keying circuit;

said keying circuit comprising a capacitor in series 4 with said keyswitch and said keying input lead, a first resistor connected between said keying input lead and a source of reference potential, a first gating element and a second resistor connected, re-' spectively, between a keyer side and a keyswitch side of said capacitor to a common terminal, a second gating element connected to said common terminal, and switching means for selectively applying to said second gating element one of said keying potential and said reference potential, and thereby to switch the mode of operation of said keying circuit between direct keying and percussion keying.

2. Apparatus as claimed in claim 1, wherein each of said gating elements comprises a single semiconductor diode.

3. In an electrical musical instrument:

a source of keying potential;

a plurality of tone generator keyers each having a keying input lead;

a plurality of keyswitches, each coupled between said source and one of said keyers;

a plurality of keying circuits, each having the structure of a percussion keying circuit and being coupled between one of said keyswitches and one of said keyers; and

keying circuit control means comprising a single switching means and a plurality of gating elements coupled to said keying circuits for simultaneously changing the mode of operation of said keying circuits from percussion keying to direct keying.

4. Apparatus as claimed in claim 3, wherein each of said keying circuits comprises:

a capacitor in series with said keyswitch and said keying input lead;

a first resistor connected between said keying input lead and a source of reference potential;

a keying circuit mode terminal;

a second resistor connected between a keyswitch side of said capacitor and said mode terminal; and

a gating element connected between a keyer side of said capacitor and said mode terminal; and said keying circuit control means further comprises:

a mode control bus;

said plurality of gating elements each being connected between said mode control bus and a mode terminal in one of said keyers; and

said switching means selectively applying to said mode control bus one of said keying potential and said reference potential.

5. Apparatus as claimed in claim 4, wherein each of said gating elements comprises a semiconductor diode. l 

1. In an electrical musical instrument: a source of keying potential; a tone generator keyer having a keying input lead; a keying circuit coupled to said keying input lead; and a keyswitch coupled between said source and said keying circuit; said keying circuit comprising a capacitor in series with said keyswitch and said keying input lead, a first resistor connected between said keying input lead and a source of reference potential, a first gating element and a second resistor connected, respectively, between a keyer side and a keyswitch side of said capacitor to a common terminal, a second gating element connected to said common terminal, and switching means for selectively applying to said second gating element one of said keying potential and said reference potential, and thereby to switch the mode of operation of said keying circuit between direct keying and percussion keying.
 2. Apparatus as claimed in claim 1, wherein each of said gating elements comprises a single semiconductor diode.
 3. In an electrical musical instrument: a source of keying potential; a plurality of tone generator keyers each having a keying input lead; a plurality of keyswitches, each coupled between said source and one of said keyers; a plurality of keying circuits, each having the structure of a percussion keying circuit and being coupled between one of said keyswitches and one of said keyers; and keying circuit control means comprising a single switching means and a plurality of gating elements coupled to said keying circuits for simultaneously changing the mode of operation of said keying circuits from percussion keying to direct keying.
 4. Apparatus as claimed in claim 3, wherein each of said keying circuits comPrises: a capacitor in series with said keyswitch and said keying input lead; a first resistor connected between said keying input lead and a source of reference potential; a keying circuit mode terminal; a second resistor connected between a keyswitch side of said capacitor and said mode terminal; and a gating element connected between a keyer side of said capacitor and said mode terminal; and said keying circuit control means further comprises: a mode control bus; said plurality of gating elements each being connected between said mode control bus and a mode terminal in one of said keyers; and said switching means selectively applying to said mode control bus one of said keying potential and said reference potential.
 5. Apparatus as claimed in claim 4, wherein each of said gating elements comprises a semiconductor diode. 